1. Field of the Invention
The present invention relates to a thin film capacitor, and an apparatus for manufacturing the same.
2. Description of the Related Art
Many kinds of capacitors are currently available and are selected for respective uses, for example, paper capacitors, electrolytic capacitors, mica capacitors, ceramic capacitors, plastic film capacitors, and so on. Among these, the plastic film capacitor is most suitable for making a thin film capacitor having minimum size and weight.
The above plastic film is widely used as a dielectric for forming the thin film capacitor; the dielectric material being, for example, organic dielectric materials such as high performance plastic films including films of polyethylene, polycarbonate, polyimide, polyterephthalate (PET) and polyphenulene sulfite (PPS), but a thin film capacitor that uses an inorganic dielectric material such as silicon oxide, although which usually exhibits a high withstand voltage, is not used widely.
An ion plating process, e.g., a plasma chemical vapor deposition (CVD) process, is superior as a process for forming an inorganic dielectric material, such as silicon oxide, into a thin film because, if an identical thin film is formed by a conventional sintering process, a high temperature of more than 1000.degree. C. is required at a substrate. Conversely, according to the above ion plating process such as, e.g., the plasma CVD process, the related temperature at the substrate can be reduced to 300.degree. C. or less, and therefore, the inorganic thin film can be easily manufactured. Further, according to the plasma CVD process, the dielectric film thickness can be very easily controlled with a high accuracy, and therefore, it is possible to obtain any dielectric constant (.epsilon.) desired.
Nevertheless, the thin film capacitor comprised of the inorganic dielectric thin film is not practical because it has a fatal defect in that, although the thin film capacitor of the inorganic dielectric may inherently provide a high withstand voltage, as expected, the manufacturing yeild thereof is extremely poor when a mass production thereof is attempted.
It has been found that the reason for the above poor yield is the occurrence of pinholes that are inevitably created inside the inorganic dielectric thin film, and this is the problem to be solved by the present invention.